1. Field of the Invention
The present invention relates, generally, to vehicle side impact performance systems. In particular, the present invention relates to a side impact protection system that is disposed within an underbody of a vehicle. And, more particularly, relates to a structural side impact protection system that is disposed under a rear passenger seat riser portion of a vehicle floor pan.
2. Description of the Related Art
Current vehicle structural designs employ a laterally disposed cross member that has a primary purpose of providing structural support during a side impact collision. When disposed in the rear of the vehicle, the cross member is commonly placed under the rear seat riser or is integrally formed therein. Manufacturing limitations require the cross members to be formed in the general shape of various rear seat and underbody components. Such limitations may degrade side impact performance since the cross member cannot be a linear piece. The governing formation component that determines the shape of the cross member is usually the rear passenger seat riser portion of the vehicle's floor pan.
Typically the outboard ends of the rear seat cushion that are connected to the rear seat riser are contoured at the door sill to follow the shape of the seat cushion. Similarly the floor pan will also follow the contoured shape of the rear seat cushion and rear seat riser thereby allowing proper ingress and egress of passengers who sit in the rear of the vehicle. By forming the shape of the floor pan to follow the contour of the rear seat cushion and seat riser, the stamping of the floor pan is greatly complicated.
More importantly, however, for side impact system purposes, the top edge of the cross member that extends laterally across the vehicle cannot be a straight piece that extends from sill to sill in the vehicle. The non-linear shape of the cross member decreases the efficiency of transferring the load from the impact side of the vehicle to the non-impact side of the vehicle when a collision occurs. Another limitation in prior art designs is that the non-linear shape of the cross member results in excessive deformation, in the form of buckling, during a side impact. Such deformation of the load bearing cross member creates undesirable energy absorption that may cause vehicle intrusion upon side impact rather than energy absorption via transfer of load to the non-impact side of the vehicle.
A further limitation in prior art designs is that the contoured cross members used cannot extend from sill to sill in the vehicle because of their arching nature. Each vehicle sill typically abuts a corresponding inner door panel, which in turn is attached to a vehicle outer door panel. The inability to extend the cross member from sill to sill prevents the cross member from receiving and transferring a load immediately upon impact. A still further limitation in prior art designs is that the inability to have the cross member extend from sill to sill in the vehicle also prevents the cross member from being raised vertically into industry standard side impact crash zones when the height of the vehicle sills are raised.